Systems, apparatus, and methods for converting a bi-level lighting system to a dimmable lighting system

ABSTRACT

A dimmable lighting system may replace a bi-level lighting system without having to modify or supplement the existing wiring between a bi-level control unit and one or more light fixtures. The dimmable lighting system may include a dimming controller that may be configured to replace a bi-level control unit in situ (i.e., e.g., in a wall-mounted dual-gang switch box). The dimmable lighting system may also include a dimming driver that may be coupled to the dimming controller via the existing wiring of the bi-level lighting system. The dimming controller may output to the dimming driver a 0-10 volt DC dimming signal referenced to an AC utility voltage. In response, a dimmable lighting device coupled to the dimming driver may output light over a wide range of dimming light levels. Methods of replacing a bi-level lighting system with a dimmable lighting system are also provided, as are other aspects.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a division of U.S. patent application Ser. No. 15/167,978, filedMay 27, 2016, now U.S. Pat. No. 9,661,714, which is a division of U.S.patent application Ser. No. 14/562,452, filed Dec. 5, 2014, now U.S.Pat. No. 9,386,648, both of which are hereby incorporated by referenceherein in their entireties for all purposes.

FIELD

The invention relates generally to lighting systems and, moreparticularly, to converting an existing bi-level lighting system to adimmable lighting system.

BACKGROUND

A bi-level lighting system (which may also be referred to as an A/Blighting system) may control lighting in an area, such as, e.g., acommercial, residential, or industrial space, and may typically providetwo levels of partial lighting between an “all lights off” state and an“all lights on” state. For example, some known bi-level lighting systemsmay have a first partial lighting level that turns on 25% of thelighting in an area (e.g., one light bulb or fluorescent tube out ofevery four) and a second partial lighting level that turns on 75% of thelighting in that area (e.g., three light bulbs or fluorescent tubes outof every four). Such bi-level lighting systems may typically include apair of switches located in, e.g., a wall-mounted dual-gang switch box.The pair of switches may be connected in the switch box to an AC utilitypower source. Associated wiring between the switch box and the lightingmay include an “A load” conductor for connecting a first switch withevery fourth light bulb or fluorescent tube, and a “B load” conductorfor connecting a second switch with the remaining three light bulbs orfluorescent tubes of every four. To turn on 25% of the lighting, thefirst switch may be activated, which connects power to 25% of thelighting, while the second switch is deactivated, which disconnectspower from the remaining 75% of the lighting. To turn on 75% of thelighting, the second switch may be activated, which connects power to75% of the lighting, while the first switch is deactivated, whichdisconnects power from the remaining 25% of the lighting. To turn on allthe lighting, both switches may be activated, which connects power toall of the lighting. And to turn off all the lighting, both switches maybe deactivated, which disconnects power from all of the lighting. Energysavings with bi-level lighting systems, however, are limited becausethey provide only two levels of partial lighting.

A dimmable lighting system may allow dimmable lighting to be dimmed toany light level between 100% (all lights fully powered) and, e.g., 15%,10%, or 0% (all lights off). Such dimmable lighting systems, therefore,provide a greater range of dimming and, thus, a greater opportunity forenergy savings while still providing a desired or acceptable level oflighting during, e.g., periods of available daylight and/ornon-occupancy. However, replacing an existing bi-level lighting systemwith a dimmable lighting system may require expensive and time consumingremoval and/or replacement of existing wiring through largelyinaccessible spaces, such as, e.g., inside walls and ceilings, in orderto connect a dimming light controller, which may replace the bi-levelswitches in a switch box, to one or more dimmable lighting devices.

Accordingly, a need exists to provide systems, apparatus, and methodsfor replacing existing bi-level lighting controls and light fixtureswith dimmable lighting controls and dimmable lighting devices withouthaving to modify and/or replace the existing wiring of the bi-levellighting system.

SUMMARY

According to one aspect, a dimming controller is provided. The dimmingcontroller comprises a voltage input connectable to a Class 1 powerconductor configured to provide an AC voltage, a ground inputconnectable to a ground conductor, a first output connectable to a firstClass 1 conductor, a second output connectable to a second Class 1conductor, a switching device coupled between the voltage input and thesecond output, and a dimming signal generator having a voltage referencecoupled to the second output and having a dimming signal output coupledto the first output. The dimming signal generator is operative toprovide a dimming signal indicative of a dimming light level at thedimming signal output, and the dimming signal is referenced to an ACvoltage received at the voltage input.

According to another aspect, a dimming driver operative to power adimmable lighting device is provided. The dimming driver comprises avoltage input connectable to a Class 1 power conductor, a neutral inputconnectable to a neutral conductor, a ground input connectable to aground conductor, a first input connectable to a first Class 1conductor, and a second input connectable to a second Class 1 conductor.The second input is coupled to the voltage input. The dimming driveralso comprises a dimming signal receiver coupled to the first input andto the second input and having an output. The dimming signal receiver isoperative to receive a dimming signal referenced to an AC voltage andoperative to provide at the output a dimming control signal indicativeof a dimming light level. The dimming driver further comprises alighting controller having an input coupled to the dimming signalreceiver output, wherein the lighting controller is operative to providepower indicative of the dimming light level to a dimmable lightingdevice.

According to a further aspect, a method of replacing a bi-level lightingsystem with a dimmable lighting system is provided. The method comprisesinstalling a dimming controller in a switch box, the dimming controllerhaving a voltage input, a first output, and a second output, wherein thedimming controller is operative to output a 0-10 volt DC dimming signalindicative of a dimming light level, and the dimming signal isreferenced to an AC voltage received at the voltage input. The methodalso comprises connecting the dimming controller to only Class 1conductors received in the switch box.

According to a still further aspect, another method of replacing abi-level lighting system with a dimmable lighting system is provided.This method comprises installing a dimming driver at a light fixturelocation, the dimming driver having a voltage input, a first input, anda second input coupled to the voltage input, wherein the dimming driveris operative to receive a 0-10 volt DC dimming signal indicative of adimming light level, and the dimming signal is referenced to an ACvoltage. The dimming driver is also operative to provide powerindicative of the dimming light level to a dimmable lighting device.This method also comprises connecting the dimming driver to only Class 1conductors received at the light fixture location.

Still other aspects, features, and advantages of the invention may bereadily apparent from the following detailed description wherein anumber of example embodiments and implementations are described andillustrated, including the best mode contemplated for carrying out theinvention. The invention may also include other and differentembodiments, and its several details may be modified in variousrespects, all without departing from the scope of the invention.Accordingly, the drawings and descriptions are to be regarded asillustrative in nature, and not as restrictive. The invention covers allmodifications, equivalents, and alternatives of the aspects disclosedherein.

BRIEF DESCRIPTION OF DRAWINGS

Persons skilled in the art will understand that the drawings, describedbelow, are for illustrative purposes only. The drawings are notnecessarily drawn to scale and are not intended to limit the scope ofthis disclosure in any way.

FIG. 1 illustrates a schematic block diagram of a bi-level lightingsystem according to the prior art.

FIG. 2 illustrates a schematic block diagram of a dimmable lightingsystem that may replace a bi-level lighting system according toembodiments.

FIG. 3 illustrates a schematic block diagram of a dimming controllerthat may be used in the dimmable lighting system of FIG. 2 according toembodiments.

FIG. 4 illustrates a schematic block diagram of a dimming driver thatmay be used in the dimmable lighting system of FIG. 2 according toembodiments.

FIG. 5 illustrates a flowchart of a method of replacing a bi-levellighting system with a dimmable lighting system according toembodiments.

FIG. 6 illustrates a flowchart of another method of replacing a bi-levellighting system with a dimmable lighting system according toembodiments.

DETAILED DESCRIPTION

Reference will now be made in detail to the example embodiments of thisdisclosure, which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

A bi-level lighting system may typically be wired with “Class 1”conductors connecting a bi-level control unit to one or more lightfixtures. “Class 1” refers to the National Electric Code (NEC) standardfor safely installing electrical wiring and equipment in high voltageapplications. For example, Class 1 circuits and wiring may be used inapplications where voltages range from about 120 volts to about 277volts AC, and in other applications, up to 600 volts. A Class 1conductor may have a wire gauge (i.e., diameter) of, e.g., 14 AWG(American Wire Gauge). The Class 1 conductors in a bi-level lightingsystem typically provide AC utility power from the bi-level control unitto the one or more light fixtures.

A dimmable lighting system is typically a low voltage system wired with“Class 2” conductors connecting a dimming controller to a dimmingdriver, which drives a dimmable lighting device. “Class 2” refers to theNEC's standard for safely installing electrical wiring and equipment inlow voltage applications. Low voltage applications may include voltagesranging up to, e.g., about 42 volts DC. A Class 2 conductor may have awire gauge of, e.g., 30-24 AWG (note that as the diameter decreases, theAWG increases). Thus, Class 2 wiring may be thinner and easier to workwith than Class 1 wiring, among other differences. The Class 2conductors in a dimmable lighting system typically provide low voltageDC power and dimming signals from a dimming controller to a dimmingdriver.

In one aspect, a bi-level lighting system may be replaced with adimmable lighting system without having to replace, remove, or modifythe existing wiring, which may comprise Class 1 conductors that connecta bi-level control unit to one or more light fixtures. A dimmingcontroller may be configured to replace a bi-level control unit in situ(e.g., in a wall-mounted switch box) and connect to the existing Class 1conductors previously connected to the bi-level control unit. Thedimming controller may output via one of the Class 1 conductors adimming signal referenced to an AC voltage instead of a typical zerovolt reference. The AC voltage may be an AC utility voltage received bythe bi-level control unit via a Class 1 power conductor. A dimmingdriver at a light fixture location may be configured to receive thedimming signal referenced to the AC voltage and, in response, drive adimmable lighting device to a dimming light level indicated by thedimming signal. In other aspects, methods of replacing a bi-levellighting system with a dimmable lighting system are provided, as will beexplained in greater detail below in connection with FIGS. 1-6.

FIG. 1 illustrates a bi-level lighting system 100 in accordance with theprior art. Bi-level lighting system 100 may include a junction box 102,a switch box 104, a bi-level control unit 106, and one or more lightfixtures 108 a and 108 b. Junction box 102 may be a metal or plasticcontainer for enclosing electrical connections and may be mounted and/orconcealed in a ceiling, under a floor, or behind an access panel. Switchbox 104 may be a wall-mounted metal or plastic container configured toenclose, e.g., a light switch, an electrical outlet, or an occupancysensor, and electrical connections thereto. In particular, switch box104 may be, e.g., a wall-mounted dual-gang switch box. A dual-gangswitch box may be configured to house, e.g., two standard lightswitches. Bi-level control unit 106 may be received in switch box 104and may include a pair of switches SW1 and SW2 and a pair of relays,Relay 1 and Relay 2. Switch SW1 may be coupled to Relay 1, and switchSW2 may be coupled to Relay 2.

AC utility power, which typically may range from 120 volts to 277 voltsfor a bi-level lighting system, may be received in junction box 102 viaa power conductor 110 (labeled V+), a neutral conductor 112, and aground conductor 114. Ground conductor 114 may be connected to an earthground. Power conductor 110 and ground conductor 114 may be received inswitch box 104 from junction box 102 and may be connected to bi-levelcontrol unit 106. In particular, power conductor 110 may be connected toboth Relay 1 and Relay 2. Relay 1 may also be connected to an A-loadconductor 116 received in switch box 104, and Relay 2 may also beconnected to a B-load conductor 118 received in switch box 104 (theseinternal connections are not shown in FIG. 1). Power conductor 110,neutral conductor 112, ground conductor 114, A-load conductor 116, andB-load conductor 118 may each be a Class 1 conductor.

Each light fixture 108 a and 108 b may receive and be connected toneutral conductor 112, ground conductor 114, A-load conductor 116, andB-load conductor 118. Each light fixture 108 a and 108 b may includeseveral light bulbs or fluorescent tubes. A-load conductor 116 mayprovide AC power and be connected to only a first group (e.g., 25%) ofthe light bulbs or fluorescent tubes of each light fixture 108 a and 108b. Conversely, B-load conductor 118 may provide AC power and beconnected to only a second, remaining group (e.g., 75%) of the lightbulbs or fluorescent tubes of each light fixture 108 a and 108 b.

Bi-level lighting system 100 may operate as follows: To turn on all thelighting of light fixtures 108 a and 108 b, a user may activate bothswitch SW1 and switch SW2. Activation of switch SW1 may cause Relay 1 toconnect AC power received from power conductor 110 to A-load conductor116, and activation of switch SW2 may cause Relay 2 to connect AC powerreceived from power conductor 110 to B-load conductor 118. Eachactivation of switch SW1 and SW2 may result in A-load conductor 116 andB-load conductor 118 respectively conducting an AC voltage of 120 voltsto 277 volts. The first and second groups of light bulbs or fluorescenttubes (i.e., all the light bulbs or fluorescent tubes) of each lightfixture 108 a and 108 b may now receive power and turn on.

To activate only the first group of light bulbs or fluorescent tubes ofeach light fixture 108 a and 108 b and thus provide a first level ofpartial lighting, switch SW1 may be activated while switch SW2 isdeactivated. Deactivation of switch SW2 may cause Relay 2 to disconnectpower from B-load conductor 118, which in turn may disconnect power fromthe second group of light bulbs or fluorescent tubes of each lightfixture 108 a and 108 b, causing them to turn off. As described above,activation of switch SW1 may connect power to A-load conductor 116,which provides power to the first group of light bulbs or fluorescenttubes of each light fixture 108 a and 108 b, causing them to turn on.

Conversely, to activate only the second group of light bulbs orfluorescent tubes of each light fixture 108 a and 108 b, and thusprovide a second level of partial lighting, switch SW2 may be activatedwhile switch SW1 is deactivated. Deactivation of switch SW1 may causeRelay 1 to disconnect power from A-load conductor 116, which in turn maydisconnect power from the first group of light bulbs or fluorescenttubes of each light fixture 108 a and 108 b, causing them to turn off.As described above, activation of switch SW2 may connect power to B-loadconductor 118, which may provide power to the second group of lightbulbs or fluorescent tubes of each light fixture 108 a and 108 b,causing them to turn on.

To turn off all the lighting of light fixtures 108 a and 108 b, a usermay deactivate both switch SW1 and switch SW2 which, as described above,disconnects power from both the first and second groups of light bulbsor fluorescent tubes of each light fixture 108 a and 108 b, causing themto turn off.

As mentioned above, energy savings with a bi-level lighting system maybe limited to the two partial levels of lighting provided thereby. Adimmable lighting system may have a greater range of dimming lightlevels and, thus, greater opportunities for saving energy when less thanfull lighting is required.

FIG. 2 illustrates a dimmable lighting system 200 in accordance with oneor more embodiments. In some embodiments, dimmable lighting system 200may replace bi-level lighting system 100 and/or a similar system withouthaving to replace, remove, supplement, and/or modify any of the existingwiring between bi-level control unit 106 and light fixtures 108 a and108 b. That is, none of the existing conductors, including powerconductor 110, neutral conductor 112, ground conductor 114, A-loadconductor 116, and B-load conductor 118 may need to be replaced,removed, supplemented, and/or modified.

Dimmable lighting system 200 may, in some embodiments, function as aClass 2 system to control dimming via 0-10 volt DC dimming controlsignals. That is, the dimming signals that control the lighting outputof a dimmable lighting device may be scaled such that a 10 volt dimmingsignal may result in 100% light output (i.e., lighting fully on), a zerovolt dimming signal may result in 0% light output (i.e., lighting off),and dimming signals between zero and 10 volts may result in variousintermediate light output levels. Note that in some embodiments,depending on the type of dimmable lighting (and associated ballasts)used, the dimming range may not go down to zero (i.e., lighting off),but may go down to only, e.g., 20%, 15%, or 10% light output, requiringa separate action (e.g., activation of a switch) to turn off thelighting completely. Thus, in some embodiments, dimmable lighting system200 may provide a dimming range of less than 0% to 100%, such as, e.g.,20% to 100%, 15% to 100%, 10% to 100%, etc. Other embodiments mayprovide other dimming ranges.

Dimmable lighting system 200 may include a dimming controller 206 andone or more dimming drivers 221 a and 221 b located at respective lightfixture locations 208 a and 208 b. Dimmable lighting system 200 may alsoinclude dimmable lighting devices 223 a and 223 b also located atrespective light fixture locations 208 a and 208 b. Light fixturelocations 208 a and 208 b may be the same locations at which lightfixtures 108 a and 108 b of bi-level lighting system 100 were located.Dimmable lighting devices 223 a and 223 b may each be LED (lightemitting diode) lighting devices. In other embodiments, dimmablelighting devices 223 a and 223 b may each be any suitable type ofdimmable lighting device, such as, e.g., CFLs (compact fluorescentlights) and/or any suitable combination of different types of dimmablelighting devices. Each pair of dimming driver and dimmable lightingdevice (e.g., dimming driver 221 a and dimmable lighting device 223 a)may be integrated as a single device, assembled from discrete componentsinto a single light fixture, or coupled together as separate parts at alight fixture location. In other embodiments, dimming drivers 221 a and221 b may be located remotely from respective dimmable lighting devices223 a and 223 b.

Dimming controller 206 may be configured to be received in switch box104, which may be, e.g., a wall-mounted dual-gang switch box. In someembodiments, dimming controller 206 may be an integral or discrete partof an occupancy sensor, light sensor, motion sensor, sound sensor,and/or like device 225 (shown in phantom) that may also be configured tobe received in switch box 104.

Dimming controller 206 may include a user interface 227 that, in someembodiments, may allow a user to, e.g., turn dimmable lighting devices223 a and 223 b on or off, set a dimmable light level, and/or programdimming controller 206 to set dimmable light levels in accordance withone or more criteria, such as, e.g., time of day, occupancy, ambientlight level, etc.

Dimming controller 206 may include a voltage input 210, a ground input214, a first output 216, and a second output 218. Voltage input 210 maybe connectable to a Class 1 power conductor configured to provide an ACvoltage. Ground input 214 may be connectable to a ground conductor,which may be coupled to earth ground. Additionally or alternatively,ground input 214 may be connectable to a neutral conductor if available.First output 216 may be connectable to a first Class 1 conductor, andsecond output 218 may be connectable to a second Class 1 conductor. Asshown in FIG. 2, upon installation of dimming controller 206 in switchbox 104, voltage input 210 may be connected to power conductor 110,ground input 214 may be connected to ground conductor 114, first output216 may be connected to A-load conductor 116, and second output 218 maybe connected to B-load conductor 118, wherein each of power conductor110, ground conductor 114, A-load conductor 116, and B-load conductor118 may be received in switch box 104. As described above, powerconductor 110, ground conductor 114, A-load conductor 116, and B-loadconductor 118 may each be a Class 1 conductor.

Dimming drivers 221 a and 221 b may each include a voltage input 220, aneutral input 222, a ground input 224, a first input 226, and a secondinput 228 (for clarity, only the inputs of dimming driver 221 a arelabeled). Voltage input 220 may be connectable to a Class 1 powerconductor. Neutral input 222 may be connectable to a neutral conductor.Ground input 224 may be connectable to a ground conductor, which may becoupled to earth ground. First input 226 may be connectable to a firstClass 1 conductor, and second input 228 may be connectable to a secondClass 1 conductor. As shown in FIG. 2, upon installation of dimmingdriver 221 a and/or 221 b at, e.g., light fixture location 208 a and/or208 b, neutral input 222 may be connected to neutral conductor 112,ground input 224 may be connected to ground conductor 114, first input226 may be connected to A-load conductor 116, and second input 228 maybe connected to B-load conductor 118. Also, voltage input 220 may beelectrically coupled to second input 228. In some embodiments, voltageinput 220 may be coupled to second input 228 prior to installation ofdimming driver 221 a or 221 b at light fixture location 208 a or 208 b.Dimming drivers 221 a and/or 221 b may also be, in some embodiments,connectable to other types of conductors, such as, e.g., Class 2conductors.

Dimmable lighting system 200 may thus be installed in place of bi-levellighting system 100 without having to replace, remove, supplement,and/or modify any existing power conductor 110, neutral conductor 112,ground conductor 114, A-load conductor 116, and/or B-load conductor 118received at switch box 104 and/or the one or more light fixtures 108 aand 108 b, and/or any existing wiring connection in junction box 102,that were used to power bi-level control unit 106 and to connectbi-level control unit 106 to the one or more light fixtures 108 a and108 b. Accordingly, the installation of dimmable lighting system 200 maybe greatly simplified and the associated costs reduced.

FIG. 3 illustrates a dimming controller 306 that may be used in dimmablelighting system 200 in accordance with one or more embodiments. Dimmingcontroller 306 may be configured to be received in switch box 104, whichin some embodiments is a wall-mounted dual-gang switch box. In someembodiments, dimming controller 306 may be an integral or discrete partof an occupancy sensor, light sensor, motion sensor, sound sensor,and/or like device that may also be configured to be received in switchbox 104. Dimming controller 306 may be configured to control an on/offlight function, a dimming light function and, in some embodiments, oneor more functions related to any one or more of the aforementionedsensors and/or like devices.

Dimming controller 306 may include a voltage input 310, a ground input314, a first output 316, and a second output 318. Voltage input 310 maybe connectable to a Class 1 power conductor configured to provide an ACvoltage. The AC voltage may range from about 120 volts to about 277volts in some embodiments and, in other embodiments, may range up toabout 347 volts. Ground input 314 may be connectable to a groundconductor, which may be an earth ground conductor (shown in phantom). Insome embodiments, ground input 314 may alternatively be connectable to aneutral conductor if available. First output 316 may be connectable to afirst Class 1 conductor, and second output 318 may be connectable to asecond Class 1 conductor. For example, referring to FIG. 2, voltageinput 310 may be connected to power conductor 110, ground input 314 maybe connected to ground conductor 114, first output 316 may be connectedto A-load conductor 116, and second output 318 may be connected toB-load conductor 118.

A switching device 330 may be coupled between voltage input 310 andsecond output 318 to electrically couple and decouple voltage input 310to and from second output 318. In some embodiments, switching device 330may be an electronic relay comprising contacts 330 a and a relay coil330 b. Switching device 330 may be an electronic relay, such as, e.g.,an RT33L12 by Tyco Electronics Corporation, of Berwyn, Pa. Othersuitable electronic relays or other suitable types of switching devicesmay be used as switching device 330.

Dimming controller 306 may also include a power supply controller 332, atransformer T1, a low voltage power supply 340, a microcontroller 347,transducers 353, a relay driver 357, and a dimming signal generator 363.Power supply controller 332 may have a line voltage input 333 that maybe coupled to voltage input 310 via a diode 334. Diode 334 may be, e.g.,an S1M_SMA type diode available from, e.g., Fairchild SemiconductorCorporation, of San Jose, Calif.

Power supply controller 332 may also have a ground input 335 that may becoupled to ground input 314. Power supply controller 332 may furtherhave a PUSH output 336, a DC output 337, and a PULL output 338 that mayeach be coupled to a primary winding P of a high frequency ferrite coretransformer T1 having a center tap, as shown in FIG. 3. Power supplycontroller 332 may rectify and filter the AC line voltage (which may be,e.g., about 120 volts, about 277 volts, or about 347 volts RMS) to about12 to 15 volts DC and apply that voltage to DC output 337, which may becoupled to the center tap of transformer T1. PUSH output 336 and PULLoutput 338 may alternately be connected to the circuit reference (e.g.,ground), such that only half of the primary winding of transformer T1 isenergized at any one time (thus, the PUSH/PULL nomenclature). This mayproduce an AC square wave first on the upper half of the primary windingP and then alternately on the lower half of the primary winding P. Thefrequency of the primary alternate operation may range from about 50 kHzto 100 kHz and the control signals may be generated by any suitablededicated microcontroller (not shown). This may result in generated ACsquare waves on the secondary winding S of transformer T1, which may besubstantially identical to the AC square waves at the primary winding Pof transformer T1 that can be used to generate an isolated low voltagepower supply. Alternatively, a resonant power converter may be usedinstead of a push-pull type power converter. Any suitable power supplycontroller may be used.

Transformer T1 may also electrically isolate voltage input 310 and powersupply controller 332 from the other components of dimming controller306 (i.e., low voltage power supply 340, microcontroller 347,transducers 353, relay driver 357, and dimming signal generator 363). Inother words, transformer T1 may prevent leakage current from finding aconduction path to earth ground. When relay contacts 330 a are closed,the AC line voltage applied at voltage input 310 is electricallyconnected to the secondary circuit reference (i.e., voltage references346, 351, 356, 360, and 367). This may ensure compliance with one ormore UL Standards, such as, e.g., UL 773. Because a neutral line istypically not available in a wall switch box, dimming controller 306 mayderive power through earth ground. In some embodiments, earth groundcurrent may be limited to 500 uA in accordance with one or moreapplicable UL standards, so any unexpected additional earth groundcurrent may cause non-compliance. Also, transformer T1 may be usedbecause this topology allows the secondary to float on AC line voltagereceived at second output 318 when relay contacts 330 a are closed. Thismay eliminate the need for an extra conductor and accordingly allowdimmable lighting system 200 to operate with only the existing A-loadconductor 116 and B-load conductor 118 of bi-level lighting system 100.

Low voltage power supply 340 may convert a received AC voltage to firstand second regulated low DC voltages (e.g., about 3.3 volts and about 12volts) that may be provided to one or more of microcontroller 347,transducers 353, relay driver 357, and/or dimming signal generator 363.Low voltage power supply 340 may have a PUSH input 341, a powerreference input 342, and a PULL input 343 that may each be coupled to asecondary winding S of transformer T1 as shown in FIG. 3. Low voltagepower supply 340 may also have a 12-volt DC output 344, a 3.3-volt DCoutput 345, and a voltage reference 346. Voltage reference 346 may becoupled to voltage input 310 via switching device 330. When switchingdevice 330 is open, voltage input 310 may not be electrically coupled tosecond output 318 and the “secondary side” (i.e., low voltage powersupply 340, microcontroller 347, relay driver 357, and dimming signalgenerator 363) may be galvanically isolated from power supply controller332. That is, the “secondary circuit reference,” comprising voltagereferences 346, 351, 356, 360, and 367, may be isolated and low voltage(conforming to, e.g., Class 2). Galvanic isolation may refer toelectrical circuits that have no direct conduction or current path therebetween, yet can still electrically communicate with each other. Such“isolated” electrical circuits may have reference voltages (commonlyzero volts or ground) that are different from each other. For example,one circuit may have a reference voltage of ground while another mayhave a positive or negative reference voltage. When switching device 330is closed, voltage input 310 may be electrically coupled to secondoutput 318 and the secondary circuit reference may be the AC linevoltage received at voltage input 310. Low voltage power supply 340 maybe, e.g., a TL431 or LP2985 power supply by Texas InstrumentsIncorporated, of Dallas, Tex. Any suitable low voltage power supply maybe used.

Microcontroller 347 may be a programmable processing device that mayinclude a processor and a memory, and may provide dimming controller 332with automatic dimming control and on/off functionality of associatedlighting coupled to dimming controller 306. That is, microcontroller 347may be programmable by a user and may have stored and/or programmableinstructions for determining, e.g., when to turn associated lighting onor off and/or when and at what dimming light level to set the associatedlighting. Microcontroller 347 may be operative to receive signals from,e.g., an occupancy sensor, a light sensor, or a user interface.Microcontroller 347 may be coupled to dimming signal generator 363 andmay be operative to control the operation of dimming signal generator363 in response to receiving those signals and/or executing storedand/or programmable instructions. For example, microcontroller 347 maybe operative to cause dimming signal generator 363 to output a dimmingsignal indicative of a predetermined dimming light level based on, e.g.,a signal representing occupancy or an ambient light level.Microcontroller 347 may include a 3.3-volt DC input 348, a relay controloutput 349, a dimming control output 350, a voltage reference 351, and atransducer input 352. The 3.3-volt DC input 348 may be coupled to the3.3-volt DC output 345 of low voltage power supply 340, and voltagereference 351 may be coupled to voltage input 310 via switching device330. Microcontroller 347 may be, e.g., an MSP430 series familymicrocontroller from Texas Instruments Incorporated, of Dallas, Tex. Anysuitable microcontroller may be used.

Transducers 353 may convert various received inputs into electricalsignals that may then be provided at an output 354 to transducer input352 of microcontroller 347. The various received inputs may include,e.g., any one or more of manual switch activations (such as, e.g., toturn lighting on or off) and/or user interface inputs (such as, e.g.,activations of various soft keys, keys on a keypad, and/or buttons to,e.g., turn lighting on or off and/or control and/or set dimming lightlevels). The various received inputs may also include, e.g., one or moresensor inputs such as, e.g., passive infrared and/or microphonic signalsfrom an occupancy sensor and/or optical signals from a light sensor.Although shown as a discrete entity, transducers 353 may represent oneor more integrated circuits or components of a user interface and/or oneor more sensors (not shown in FIG. 3) associated with or comprisingdimming controller 306. Transducers 353 may also include a 3.3-volt DCinput 355 and a voltage reference 356. The 3.3-volt DC input 355 may becoupled to the 3.3-volt DC output 345 of low voltage power supply 340,and voltage reference 356 may be coupled to voltage input 310 viaswitching device 330.

Relay driver 357 may include a 12-volt DC input 358, a relay controlinput 359, a voltage reference 360, a relay coil A output 361 and arelay coil B output 362. The 12-volt DC input 358 may be coupled to the12-volt DC output 344 of low voltage power supply 340, and voltagereference 360 may be coupled to voltage input 310 via switching device330. Relay coil A output 361 and relay coil B output 362 may be coupledto relay coil 330 b. Relay control input 359 may be coupled to relaycontrol output 349 of microcontroller 347. Relay driver 357 may beoperative to cause switching device 330 to electrically couple voltageinput 310 to second output 318 in response to a signal received frommicrocontroller 347. That is, upon receipt of a relay activation signalat relay control input 359 from relay control output 349 ofmicrocontroller 347, relay driver 357 may energize coil 330 b causingcontacts 330 a to close. This may electrically couple voltage input 310to second output 318, which may provide AC power received at voltageinput 310 to associated lighting via, e.g., B-load conductor 118. Thismay also provide an AC voltage received at voltage input 310 to voltagereferences 346, 351, 356, 360, and 367, the result of which is describedbelow in connection with dimming signal generator 363.

The relay activation signal from microcontroller 347 may have resultedin response to an occurrence of a manual lighting switch activationsignal received at transducer input 352 of microcontroller 347, apre-programmed event, such as, e.g., a particular time of day, or asensor signal (indicating, e.g., occupancy or a low ambient light level)received at transducer input 352 of microcontroller 347. Similarly, arelay deactivation signal may be received at relay control input 359from relay control output 349 of microcontroller 347. A deactivationsignal may de-energize coil 330 b, causing contacts 330 a to open. Thismay disconnect AC power to associated lighting via, e.g., B-loadconductor 118, causing associated lighting to turn off (i.e., 0% lightoutput). Relay driver 357 may be a discrete design using transistors andresistors as is known in the art. Any suitable relay driver may be used.

Dimming signal generator 363 may include a 3.3-volt DC input 364, a12-volt DC input 365, a dimming control input 366, a voltage reference367, and a dimming signal output 368. The 3.3-volt DC input 364 may becoupled to the 3.3-volt DC output 345 of low voltage power supply 340,and the 12-volt DC input 365 may be coupled to the 12-volt DC output 344of low voltage power supply 340. Voltage reference 367 may be coupled tovoltage input 310 via switching device 330. Dimming control input 366may be coupled to dimming control output 350 of microcontroller 347, anddimming signal output 368 may be coupled to first output 316.

Dimming control input 366 may receive dimming control signals frommicrocontroller 347. The dimming control signals may indicate a dimminglight level (e.g., from a 0% light level to a 100% light level in someembodiments) based on, e.g., signals received by microcontroller 347 viatransducers 353 from one or more sensors and/or a user interface, suchas, e.g., user interface 227 of FIG. 1. Thus, e.g., a user interface maybe coupled (indirectly) to dimming signal generator 363 and may beoperative to receive inputs indicating a desired on/off state oflighting, a dimming light level, or both. This may result in a dimmingsignal indicative of that on/off state and/or dimming light level to beoutput from dimming signal output 368 and first output 316.

Dimming signal generator 363 may be operative to provide a dimmingsignal indicative of a dimming light level at dimming signal output 368.In some embodiments, dimming signal generator 363 may employ 0-10 voltDC dimming control signaling to control the dimming light level ofassociated dimmable lighting, as described above in connection withdimming controller 206. However, in order to use only the existingA-load conductor 116 and B-load conductor 118 typically available atswitch box 104 after removal of bi-level control unit 106, withouthaving to install one or more additional signaling conductors to carrythe 0-10 volt DC dimming signals, the dimming signal may be referencedto an AC voltage received at voltage input 310. That is, upon theclosing of switching device 330 to electrically couple voltage input 310to second output 318, an AC voltage received at voltage input 310 may beprovided to voltage references 346, 351, 356, 360, and 367 instead of,e.g., a zero voltage or ground reference. Dimming signals provided atdimming signal output 368 may therefore be referenced to, or floatingon, an AC voltage received at voltage input 310, which may alsoconcurrently provide power to an associated dimming driver and dimmablelighting devices. Thus, additional wiring may not be needed wheninstalling dimming controller 306. Dimming signal generator 363 may be,e.g., constructed discretely using op-amps, transistors, resistors, andcapacitors as is known in the art. Any suitable dimming signal generatormay be used.

FIG. 4 illustrates a dimming driver 421 that may be used in dimmablelighting system 200 in accordance with one or more embodiments. Dimmingdriver 421 may be operative to drive a dimmable lighting device and maybe located at a light fixture location that may have been used by alight fixture of a bi-level lighting system, such as, e.g., lightfixture 108 a or 108 b of bi-level lighting system 100. Dimming driver421 may alternatively be located at any suitable location. In someembodiments, dimming driver 421 and a dimmable lighting device may beintegrated into a single device. In other embodiments, dimming driver421 and a dimmable lighting device may be assembled from discretecomponents into a single light fixture or, alternatively, each may beinstalled at a light fixture location and coupled to each other asseparate parts. In still other embodiments, dimming driver 421 may belocated remotely from a dimmable lighting device. The dimmable lightingdevice may be, e.g., dimmable lighting device 223 a or 223 b of FIG. 2and, in some embodiments, may be a bank of LEDs, CFLs, or other suitabletype or suitable combinations of dimmable lighting devices.

Dimming driver 421 may include a voltage input 420, a neutral input 422,a ground input 424, a first input 426, a second input 428, a lightingdevice voltage+output 498, and a lighting device voltage−output 499.Lighting device voltage+output 498 and lighting device voltage−output499 may be coupled to a dimmable lighting device (not shown in FIG. 4),such as, e.g., dimmable lighting device 223 a or 223 b of FIG. 2.Voltage input 420 may be connectable to a Class 1 power conductor.Neutral input 422 may be connectable to a neutral conductor, and groundinput 424 may be connectable to a ground conductor, which may be coupledto earth ground. First input 426 may be connectable to a first Class 1conductor, and second input 428 may be connectable to a second Class 1conductor. For example, upon installation of dimming driver 421 at lightfixture location 208 a or 208 b, neutral input 422 may be connected toneutral conductor 112, ground input 424 may be connected to groundconductor 114, first input 426 may be connected to A-load conductor 116,and second input 428 may be connected to B-load conductor 118. In someembodiments, first input 426 may be coupled to first output 316 ofdimming controller 306 via a first Class 1 conductor routed from awall-mounted switch box to a light fixture location at which dimmingdriver 421 is located. Similarly, second input 428 may be coupled tosecond output 318 of dimming controller 306 via a second Class 1conductor routed from the wall-mounted switch box to the light fixturelocation. Also, voltage input 420 may be electrically coupled to secondinput 428 (not shown in FIG. 4). In some embodiments, voltage input 420may be coupled to second input 428 prior to installation of dimmingdriver 421 at a light fixture location.

Dimming driver 421 may also include a line filter 470, a switching powercontroller 475, a transformer T2, a dimming power supply 480, a dimmingsignal receiver 483, a lighting power supply 488, a lighting controller491, and optical isolators 496 and 497. As described in more detailbelow, line filter 470 and switching power controller 475 may begalvanically isolated from dimming power supply 480, dimming signalreceiver 483, lighting power supply 488, and lighting controller 491.Dimming power supply 480 and dimming signal receiver 483 may begalvanically isolated from line filter 470, switching power controller475, lighting power supply 488, and lighting controller 491. Andlighting power supply 488 and lighting controller 491 may begalvanically isolated from line filter 470, switching power controller475, dimming power supply 480, and dimming signal receiver 483.

Line filter 470 may have a line voltage filter input 471, a neutralinput 472, and a ground input 473. Line voltage filter input 471 may becoupled to voltage input 420, neutral input 472 may be coupled toneutral input 422, and ground input 473 may be coupled to ground input424. Line filter 470 may also have a line voltage filter output 474 aand a reference voltage output 474 b. Line filter 470 may be used toprevent high frequency noise that may be generated by switching powercontroller 475 from coupling back onto an AC power line connected tovoltage input 420, which may potentially interfere with other equipmentsharing the same power. Line filter 470 may also provide a DC voltage toswitching power controller 475. The DC voltage may be a function of theAC line voltage received at voltage input 420 and the load on thesecondary side (S1 and S2) of transformer T2. For example, if the ACline voltage is about 120 volts, the output DC voltage may be about 169volts. If the AC line voltage is, e.g., about 277 volts, the output DCvoltage may be about 390 volts. Line filter 470 may be constructed fromdiscrete parts to provide common and differential mode filtering, as isknown in the art. Any suitable line filter may be used.

Switching power controller 475 may have a line voltage input 476 a, avoltage reference 476 b, a feedback input 477, a voltage bulk output478, and a MOSFET output 479. Line voltage input 476 a may be coupled toline voltage filter output 474 a, and voltage reference 476 b may becoupled to reference voltage output 474 b. Switching power controller475 may receive DC voltage from line filter 470 and apply an AC squarewave with a varying pulse width to drive the primary winding P oftransformer T2 via voltage bulk output 478 and MOSFET output 479. Thatis, voltage bulk output 478 and MOSFET output 479 may each be coupled toa primary winding P of transformer T2, which may be a high frequencyferrite core transformer. In some embodiments, a switching frequency ofabout 100 kHz may be used. Other switching frequencies may be used inother embodiments. Switching power controller 475 may be, e.g., anIRS2548D by International Rectifier, of El Segundo, Calif. Any suitableswitching power controller may be used.

Transformer T2 may have a first secondary winding S1 and a secondsecondary winding S2. Transformer T2 may convert the AC voltage receivedfrom switching power controller 475 to one or more lower AC voltages ina range of, e.g., about 12 to 20 volts at the first secondary winding S1and in a range of, e.g., about 25 to 40 volts at the second secondarywinding S2. Transformer T2 may electrically isolate voltage input 420,line filter 470, and switching power controller 475 from the othercomponents of dimming driver 421. That is, transformer T2 may prevent ACvoltage received at voltage input 420 from finding a conduction path tothe other components of dimming driver 421.

Dimming power supply 480 may have a dimming power A input 481 a, adimming power B input 481 b, a dimming voltage output 482 a, and adimming voltage reference 482 b. Dimming power A input 481 a and dimmingpower B input 481 b may be coupled to the first secondary winding S1 oftransformer T2. The voltage received from the first secondary winding S1may, in some embodiments, be about 12 to 20 volts AC. Dimming powersupply 480 may convert an AC voltage received from transformer T2 into aregulated DC voltage provided at dimming voltage output 482 a. The DCvoltage provided may, in some embodiments, be about 16 volts. Thedimming reference voltage provided at dimming voltage reference 482 bmay, in some embodiments, be about zero volts. Dimming power supply 480may be, e.g., an LP2985 by Texas Instruments Incorporated, of Dallas,Tex. Any suitable dimming power supply may be used.

Dimming signal receiver 483 may have a dimming voltage input 484 a, adimming voltage reference 484 b, a dimming control output 485, a0-10V+input 486, and a 0-10V−input 487. Dimming voltage input 484 a maybe coupled to dimming voltage output 482 a of dimming power supply 480,and dimming voltage reference 484 b may be coupled to dimming voltagereference 482 b of dimming power supply 480. The 0-10V+input 486 may becoupled to first input 426, and the 0-10V−input 487 may be coupled tosecond input 428 of dimming driver 421. Second input 428 may be coupledto provide a reference voltage for dimming power supply 480 and dimmingsignal receiver 483.

Dimming signal receiver 483 may be operative to receive a dimming signalreferenced to an AC voltage and indicative of a dimming light level(e.g., from 0% light output to 100% light output in some embodiments) atthe 0-10V+input 486 and the 0-10V−input 487. The dimming signal may bereceived via first input 426 and second input 428 and may have beenoutput from a dimming controller, such as, e.g., dimming controller 206or 306 and, more particularly, from a dimming signal generator such as,e.g., dimming signal generator 363. Dimming signal receiver 483 may beoperative to provide at dimming control output 485 a dimming controlsignal indicative of a dimming light level. That is, a dimming controlsignal based on the dimming signal received at the 0-10V+input 486 andthe 0-10V−input 487 may be provided at dimming control output 485. Insome embodiments, dimming driver 421 may respond to receiving the 0-10volt control voltage in accordance with a linear or logarithmic dimmingcurve or light output, as is known in the art.

An optical isolator 496 may be coupled between dimming signal receiver483 and lighting controller 491. That is, an input of optical isolator496 may be coupled to dimming control output 485 of dimming signalreceiver 483 and an output of optical isolator 496 may be coupled tolighting controller 491. Optical isolator 496 may provide galvanicisolation between dimming signal receiver 483 and lighting controller491. Optical isolator 496 may be, e.g., an LTV-817 by Lite-On TechnologyCorporation, of Taipei, Taiwan. Any suitable optical isolator may beused.

Lighting power supply 488 may have a lighting power A input 489 a, alighting power B input 489 b, a lighting voltage output 490 a, and alighting voltage reference 490 b. Lighting power A input 489 a andlighting power B input 489 b may be coupled to second secondary windingS2 of transformer T2. The voltage received from the second secondarywinding S2 may, in some embodiments, be about 40 volts AC. Lightingpower supply 488 may convert an AC voltage received from transformer T2into a regulated DC voltage provided at lighting voltage output 490 a.The DC voltage provided may, in some embodiments, be about 40 volts. Thelighting reference voltage at lighting voltage reference 490 b may, insome embodiments, be about zero volts. Any suitable lighting powersupply may be used.

Lighting controller 491 may have a lighting voltage input 492 a, alighting voltage reference 492 b, a lighting control input 493, alighting voltage+output 494, and a lighting voltage−output 495. Lightingvoltage input 492 a may be coupled to lighting voltage output 490 a oflighting power supply 488, and lighting voltage reference 492 b may becoupled to lighting voltage reference 490 b of lighting power supply488. Lighting voltage+output 494 may be coupled to lighting devicevoltage+output 498 of dimming driver 421, and lighting voltage−output495 may be coupled to a lighting device voltage−output 499 of dimmingdriver 421. Lighting device voltage−output 499 may be coupled to providea reference voltage for lighting power supply 488 and lightingcontroller 491.

Lighting control input 493 may be coupled to dimming control output 485of dimming signal receiver 483 via optical isolator 496. That is,lighting control input 493 may be coupled to the output of opticalisolator 496 to optically receive a dimming control signal from dimmingcontrol output 485 of dimming signal receiver 483. The dimming controlsignal received at lighting control input 493 may be the absolute lightlevel to which lighting controller 491 may set outputs 494 and 495. Foran LED bank, e.g., this may be done by limiting the amount of currentflowing to the LED bank. The amount of current may be limited byproviding feedback through optical isolator 497 to switching powercontroller 475, which may reduce power.

Optical isolator 497 may be coupled between feedback input 477 ofswitching power controller 475 and lighting voltage output 490 a oflighting power supply 488. That is, optical isolator 497 may have anoutput coupled to feedback input 477 of switching power controller 475,and an input coupled to a node between lighting voltage output 490 a andlighting voltage input 492 a. Optical isolator 497 may providegalvanically isolated feedback from lighting voltage output 490 a toswitching power controller 475. This may allow switching powercontroller 475 to adjust its pulse width in response to changes in thesecondary load. Optical isolator 497 may be the same part or type asoptical isolator 496 or, alternatively, may be any suitable part or typeof optical isolator.

Note that none of switching power controller 475, dimming signalreceiver 483, and lighting controller 491 shares a common referencevoltage.

FIG. 5 illustrates a method 500 of replacing a bi-level lighting systemwith a dimmable lighting system. In some embodiments, the bi-levellighting system may be similar or identical to bi-level lighting system100. In some embodiments, the dimmable lighting system may be dimmablelighting system 200 of FIG. 2. The dimmable lighting system may providea dimming range of, e.g., 20% to 100%, 15% to 100%, 10% to 100%, or 0%to 100%. That is, dimming light levels may range from maximum lightoutput (i.e., 100%) down to, e.g., 20% light output, 15% light output,10% light output, or 0% light output (i.e., lights off), respectively.Other embodiments may have other dimming ranges.

At process block 502, method 500 may include installing a dimmingcontroller in a switch box. In some embodiments, the switch box may be awall-mounted dual-gang switch box previously housing a bi-level controlunit (including, e.g., a pair of switches and relays as described inconnection with FIG. 1). The dimming controller may have a voltageinput, a first output, and a second output, and may be operative tooutput a 0-10 volt DC dimming signal indicative of a dimming lightlevel. The dimming signal may be referenced to an AC voltage received atthe voltage input. That is, instead of a typical ground reference, thedimming controller may use the AC voltage received at the voltage inputas the reference voltage for the dimming signal. This may eliminate theneed for an additional signal wire from the dimming controller. Thedimming controller may be, e.g., dimming controller 206 or 306 of FIG. 2or 3, respectively.

At process block 504, method 500 may include connecting the dimmingcontroller to only Class 1 conductors received in the switch box. Insome embodiments, the voltage input of the dimming controller may beconnected to a Class 1 power conductor received in the switch box andconfigured to provide an AC voltage from a utility power source to theswitch box. The first output of the dimming controller may be connectedto a first Class 1 conductor received in the switch box, and the secondoutput of the dimming controller may be connected to a second Class 1conductor received in the switch box. The Class 1 power conductor, thefirst Class 1 conductor, and the second Class 1 conductor may each havebeen previously connected to the bi-level control unit of the bi-levellighting system being replaced. For example, the Class 1 power conductormay be power conductor 110, the first Class 1 conductor may be A-loadconductor 116, and the second Class 1 conductor may be B-load conductor118 of FIGS. 1 and 2.

In some embodiments, method 500 may also include one or more of thefollowing: removing the bi-level control unit of the bi-level lightingsystem being replaced from the switch box prior to the installing of thedimming controller, and/or connecting a ground input of the dimmingcontroller to an earth ground conductor received in the switch box. Forexample, the bi-level control unit may be bi-level control unit 106 ofFIG. 1, and the earth ground conductor may be ground conductor 114

Method 500 may also include, in some embodiments, installing a dimmingdriver at a light fixture location, the dimming driver operative toreceive the 0-10 volt DC dimming signal indicative of a dimming lightlevel. The dimming driver may also be operative to provide powerindicative of the dimming light level to a dimmable lighting device.Method 500 may further include connecting the dimming driver to only theClass 1 conductors received at the switch box and routed to the lightfixture location.

FIG. 6 illustrates a second method 600 of replacing a bi-level lightingsystem with a dimmable lighting system. In some embodiments, thebi-level lighting system may be similar or identical to bi-levellighting system 100. In some embodiments, the dimmable lighting systemmay be dimmable lighting system 200 of FIG. 2. The dimmable lightingsystem may provide a dimming range of, e.g., 20% to 100%, 15% to 100%,10% to 100%, or 0% to 100%. That is, dimming light levels may range frommaximum light output (i.e., 100%) down to, e.g., 20% light output, 15%light output, 10% light output, or 0% light output (i.e., lights off),respectively. Other embodiments may have other dimming ranges.

At process block 602, method 600 may include installing a dimming driverat a light fixture location. In some embodiments, the light fixturelocation may have had non-dimmable lighting mounted or attached thereat,which may be replaced with one or more suitable dimmable lightingdevices. The dimming driver may have a voltage input, a first input, anda second input, wherein the second input may be coupled to the voltageinput. The dimming driver may be operative to receive a 0-10 volt DCdimming signal indicative of a dimming light level, wherein the dimmingsignal may be referenced to an AC voltage, wherein the AC voltage may bereceived at the voltage input. The dimming driver may also be operativeto provide power indicative of the dimming light level to a dimmablelighting device. The dimming driver may be, e.g., dimming driver 221 aor 221 b of FIG. 2, or dimming driver 421 of FIG. 4.

At process block 604, method 600 may include connecting the dimmingdriver to only Class 1 conductors received at the light fixturelocation. In some embodiments, the first input of the dimming driver maybe connected to a first Class 1 conductor received at the light fixturelocation, and the second input of the dimming driver may be connected toa second Class 1 conductor received at the light fixture location. Thefirst Class 1 conductor and the second Class 1 conductor may each havebeen previously connected to a light fixture having non-dimmablelighting. For example, the first Class 1 conductor may be A-loadconductor 116, and the second Class 1 conductor may be B-load conductor118 of FIGS. 1 and 2.

In some embodiments, method 600 may also include connecting a groundinput of the dimming driver to an earth ground conductor received at thelight fixture location, and connecting a neutral input of the dimmingdriver to a neutral conductor received at the light fixture location.For example, the neutral conductor may be neutral conductor 112 and theearth ground conductor may be ground conductor 114 of FIGS. 1 and 2.

Method 600 may also include, in some embodiments, installing a dimmingcontroller in a switch box, the dimming controller operative to outputthe 0-10 volt DC dimming signal indicative of a dimming light level.Method 600 may further include connecting the dimming controller to onlythe Class 1 conductors routed from the light fixture location to theswitch box.

Note that some embodiments, or portions thereof, may be provided as acomputer program product or software that may include a machine-readablemedium having non-transient instructions stored thereon, which may beused to program, e.g., microcontroller 347 or other electronic device toperform a process in accordance with one or more embodiments.

Persons skilled in the art should readily appreciate that the inventiondescribed herein is susceptible of broad utility and application. Manyembodiments and adaptations of the invention other than those describedherein, as well as many variations, modifications, and equivalentarrangements, will be apparent from, or reasonably suggested by, theinvention and the foregoing description thereof, without departing fromthe substance or scope of the invention. For example, although describedin connection with dimmable LED lighting devices and the replacement ofa bi-level lighting system, one or more embodiments of the invention mayinvolve other types of dimmable lighting devices and/or installations ofdimmable lighting systems that do not involve the replacement of anexisting bi-level lighting system. For example, a dimmable lightingsystem of the invention may be installed in new construction using lesswiring than conventional dimmable lighting systems. Accordingly, whilethe invention has been described herein in detail in relation tospecific embodiments, it should be understood that this disclosure isonly illustrative and presents examples of the invention and is mademerely for purposes of providing a full and enabling disclosure of theinvention. This disclosure is not intended to limit the invention to theparticular apparatus, devices, assemblies, systems, or methodsdisclosed, but, to the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the scope ofthe invention.

What is claimed is:
 1. A method of replacing a bi-level lighting systemwith a dimmable lighting system, the method comprising: installing adimming controller in a switch box, the dimming controller having avoltage input, a first output, and a second output, the dimmingcontroller operative to output a dimming signal at the first outputindicative of a dimming light level, the dimming signal referenced to anAC voltage received at the voltage input; and connecting the dimmingcontroller to only Class 1 conductors received in the switch box.
 2. Themethod of claim 1, wherein the installing comprises installing thedimming controller in a wall-mounted dual-gang switch box.
 3. The methodof claim 1, wherein the dimming signal comprises a 0-10 volt DC dimmingsignal indicative of a dimming light level and referenced to the ACvoltage received at the voltage input.
 4. The method of claim 1, furthercomprising removing a bi-level control unit from the switch box prior tothe installing of the dimming controller.
 5. The method of claim 1,further comprising, prior to the installing, providing the dimmingcontroller having a dimming signal generator, the dimming signalgenerator including a voltage reference coupled to the second output andincluding a dimming signal output coupled to the first output, thedimming signal generator operative to provide the dimming signal at thedimming signal output.
 6. The method of claim 1, further comprising,prior to the installing, providing the dimming controller having: aswitching device coupled between the voltage input and the secondoutput; a power supply controller coupled to the voltage input; atransformer having a primary winding coupled to an output of the powersupply controller; and a low voltage power supply having an input and anoutput, the input coupled to a secondary winding of the transformer andthe output coupled to the dimming signal generator, the low voltagepower supply galvanically isolated from the power supply controller inresponse to the switching device electrically decoupling the voltageinput from the second output.
 7. The method of claim 1, wherein theconnecting of the dimming controller comprises: connecting the voltageinput to a Class 1 power conductor received in the switch box andconfigured to provide an AC voltage from a power source to the switchbox; connecting the first output of the dimming controller to a firstClass 1 conductor received in the switch box; and connecting the secondoutput of the dimming controller to a second Class 1 conductor receivedin the switch box.
 8. The method of claim 1, wherein the dimmingcontroller further comprises a ground input, and the method furthercomprises connecting the ground input to an earth ground conductorreceived in the switch box.
 9. The method of claim 1, furthercomprising: installing a dimming driver at a light fixture location, thedimming driver operative to receive the dimming signal indicative of adimming light level, the dimming driver also operative to provide powerindicative of the dimming light level to a dimmable lighting device; andconnecting the dimming driver to only the Class 1 conductors received atthe switch box and routed to the light fixture location.
 10. The methodof claim 1, further comprising installing a dimmable lighting device ata light fixture location.
 11. A method of replacing a bi-level lightingsystem with a dimmable lighting system, the method comprising:installing a dimming driver at a light fixture location, the dimmingdriver having a voltage input, a first input, and a second input coupledto the voltage input, the dimming driver operative to receive a dimmingsignal at the first input indicative of a dimming light level, thedimming signal referenced to an AC voltage, the dimming driver alsooperative to provide power indicative of the dimming light level to adimmable lighting device; and connecting the dimming driver to onlyClass 1 conductors received at the light fixture location.
 12. Themethod of claim 11, wherein the dimming signal comprises a 0-10 volt DCdimming signal referenced to the AC voltage.
 13. The method of claim 11,further comprising, prior to the installing, providing the dimmingdriver having: a dimming signal receiver coupled to the first input andto the second input and having an output, the dimming signal receiveroperative to receive a dimming signal referenced to the AC voltage andoperative to provide at the dimming signal receiver output a dimmingcontrol signal indicative of a dimming light level; and a lightingcontroller having an input coupled to the dimming signal receiveroutput, the lighting controller operative to provide the powerindicative of the dimming light level to the dimmable lighting device.14. The method of claim 13, wherein the providing of the dimming driverfurther comprises providing the dimming driver further having an opticalisolator coupled between the dimming signal receiver output and thelighting controller input.
 15. The method of claim 11, wherein theconnecting of the dimming driver comprises: connecting the first inputof the dimming driver to a first Class 1 conductor received at the lightfixture location; and connecting the second input of the dimming driverto a second Class 1 conductor received at the light fixture location.16. The method of claim 11, wherein the dimming driver further comprisesa ground input and a neutral input, and the method further comprisesconnecting the ground input to an earth ground conductor received at thelight fixture location and connecting the neutral input to a neutralconductor received at the light fixture location.
 17. The method ofclaim 11, further comprising installing a dimmable lighting device atthe light fixture location.
 18. The method of claim 17, furthercomprising connecting the dimmable lighting device to the dimming driverat the light fixture location.
 19. The method of claim 17, furthercomprising removing a non-dimmable lighting device from the lightfixture location prior to the installing of the dimmable lightingdevice.
 20. The method of claim 11, further comprising: installing adimming controller in a switch box, the dimming controller operative tooutput the dimming signal indicative of a dimming light level; andconnecting the dimming controller to only the Class 1 conductors routedfrom the light fixture location to the switch box.